CN101075830A - Method for determining down initial transmitting power - Google Patents

Abstract

The invention discloses a method for determining the downlink initial transmission power, the key of which is that the factors of path loss and time slot interference are taken into account when calculating the downlink initial transmission power, and the size of the downlink initial transmission power is reasonably calculated, thereby avoiding The impact caused by the initial transmission power being too large or too small. In the process of just establishing a physical channel or channel reassignment or handover, even if there is no target time slot interference measurement value reported by the UE, the method of the present invention can be used to calculate the downlink time slot interference, and the downlink open-loop power control can be used to calculate the downlink initial The transmission power ensures the UE's access success rate and service QoS quality requirements, and at the same time avoids causing large interference to other UEs. In this way, the coverage area and capacity of the network can be improved, and the performance of the system can be improved.

Description

Method for determining downlink initial transmit power

technical field

The present invention relates to a communication system, in particular to a method for determining downlink initial transmission power.

Background technique

Code Division Multiple Access (CDMA) is a modulation and multiple access technology based on spread spectrum communication. In a CDMA communication system, since the base station and the mobile station use the same wireless frequency band, the base station will transmit signals to a certain mobile station. Cause interference to mobile stations in this cell and neighboring cells. Since the CDMA mobile communication system is a self-interference system with limited interference and has the characteristics of near-far effect, in order to maximize the capacity and coverage of the system and ensure the quality of service communication, the base station (Node B) needs to allocate reasonable downlink power.

In Time Division-Synchronous Code Division Multiple Access (TD-SCDMA) system, according to the division of power control functions in the system, power control is divided into open-loop power control, inner-loop power control and outer-loop power control. When the physical channel is just established or the channel is reconfigured, such as initial access, handover to a new cell, etc., the transmitter cannot obtain the feedback of the reception quality and interference from the receiver in advance, so open-loop power control is used to calculate the initial transmit power.

In the uplink open-loop power control, the Node B can measure the uplink time slot interference, that is, the Interference Signal Code Power (ISCP, Interference Signal Code Power), and the user terminal (UE) measures the downlink path loss L. According to the measured ISCP and L, through the uplink The open-loop power control can calculate the uplink initial transmit power. But in the downlink, when the physical channel is just established or the channel is reconfigured during the handover process, the UE cannot measure the downlink time slot interference in advance.

The downlink time slot interference is mainly related to the distance between the UE and the Node B of the base station and the system load. If the distance between the UE and the base station is relatively large, that is, the UE is at the edge of the cell and the load of the surrounding adjacent cells is relatively large, the UE suffers The interference of adjacent cells is relatively large; if the distance between the UE and the base station is relatively small, that is, the UE is located in the center of the cell and the load of the surrounding adjacent cells is relatively light, the interference suffered by the UE will be relatively small.

The existing implementation method is that the downlink initial transmission power is evenly distributed according to the maximum transmission power of the downlink time slot. Suppose the maximum transmit power of the downlink time slot of the base station is P _DL-MAX , and there are N basic resource units (BRUs) in the downlink time slot. If the service accessed by the UE occupies m BRUs, the initial downlink power allocated to the UE is: $P_{\mathrm{DL}}=\frac{m}{N}\·P_{\mathrm{DL}-\mathrm{MAX}}.$

The existing downlink initial power allocation method does not consider downlink path loss and downlink time slot interference, so the allocated downlink initial transmit power is very inaccurate. If the UE is relatively close to the base station, the path loss is relatively small at this time, and the interference to the UE from the surrounding adjacent cells will be relatively small. If the downlink power allocated according to the current average is much greater than the appropriate initial downlink transmit power, it is Other UEs cause a large burst of interference impact, resulting in a sudden deterioration of the quality of other UEs or even call drop, and will reduce the coverage and capacity of the cell. If the UE is far away from the base station, the path loss will be relatively large at this time, and the interference to the UE from the surrounding adjacent cells will also be relatively large. According to the current average distribution of downlink power, the size of the downlink initial transmission power will be less than the appropriate initial downlink transmission power, resulting in the UE Initial access failure or UE handover failure.

Contents of the invention

In view of this, the purpose of the present invention is to provide a method for determining initial downlink transmission power, which takes into account downlink path loss and downlink time slot interference.

To achieve the above object, the technical scheme of the present invention is as follows:

A method for determining downlink initial transmit power, comprising the following steps:

a. Calculating the downlink path loss for the base station signal to reach the location of the user terminal UE;

b. Determine the downlink time slot interference value of the UE according to the downlink path loss and loads of surrounding cells;

c. Calculate the downlink initial transmit power according to the downlink time slot interference value.

Preferably, the method for calculating the downlink path loss described in step a is:

The received power PCCPCH RSCP of the PCCPCH received by the UE is subtracted from the reference transmit power PTX _PCCPCH of the basic public control channel PCCPCH, and the obtained difference is the downlink path loss.

Preferably, the process of determining downlink time slot interference in step b includes:

A list of preset downlink time slot interference matrices, which includes the correspondence between the distance S between the UE and the base station, the downlink time slot load level D of surrounding adjacent cells, and the downlink time slot interference;

Estimate the current distance S between the UE and the base station according to the downlink path loss, and estimate the downlink time slot load level D of the UE's current adjacent cell according to the downlink time slot load Ld of the adjacent cell; by querying the correspondence of the downlink time slot interference matrix list The downlink time slot interference of the UE is obtained.

Preferably, the process of estimating the distance S between the UE and the base station according to the downlink path loss includes:

Preset downlink path loss thresholds {L ₁ , L ₂ , ..., L _n-1 } including one or more downlink path loss values; divide the downlink path loss thresholds into at least one category in a certain order, each The class corresponds to a distance S, and each class corresponds to a downlink path loss threshold interval;

Calculate the current downlink path loss value L of the UE, determine the threshold interval where the current downlink path loss value L of the UE is located according to the downlink path loss threshold, and then obtain the distance S between the UE and the base station according to the threshold interval.

Preferably, the process of estimating the downlink time slot load level D of the current neighboring cell of the UE according to the downlink time slot load Ld of the neighboring cell includes:

Preset the downlink timeslot load threshold {Ld ₁ , Ld ₂ ,...Ld _m-1 } including one or more downlink timeslot load values; classify the downlink timeslot load thresholds into at least one category in a certain order, Each category corresponds to a downlink slot load level D, and each category corresponds to a downlink path loss threshold interval;

Calculate the current downlink timeslot load Ld of the UE, determine the threshold interval where the current downlink timeslot load Ld of the UE is located according to the downlink timeslot load threshold, and then obtain the current downlink timeslot load level D according to the threshold interval.

Preferably, the method for calculating the UE's current downlink time slot load Ld is:

$\mathrm{<span\; class="notranslate">\; Ld</span>}<span\; class="notranslate">\; =</span>\underset{\mathrm{<span\; class="notranslate">\; i</span>}<span\; class="notranslate">\; =</span>\mathrm{<span\; class="notranslate">\; 1</span>}}{\overset{\mathrm{<span\; class="notranslate">\; N</span>}}{\mathrm{<span\; class="notranslate">\; \&Sigma;</span>}}}{\mathrm{<span\; class="notranslate">\; \&alpha;</span>}}_{\mathrm{<span\; class="notranslate">\; i</span>}}<span\; class="notranslate">\; \&Center\; Dot;</span>{\mathrm{<span\; class="notranslate">\; Ld</span>}}_{\mathrm{<span\; class="notranslate">\; i</span>}}$

Wherein, Ld _i is the downlink time slot load of the i-th neighboring cell, α _i is the weighting coefficient of the downlink time slot load of the neighboring cell on UE downlink time slot interference; N is the number of neighboring cells.

Preferably, the method for calculating the UE's current downlink time slot load Ld is:

$\mathrm{<span\; class="notranslate">\; Ld</span>}<span\; class="notranslate">\; =</span>\mathrm{<span\; class="notranslate">\; \&alpha;</span>}<span\; class="notranslate">\; \&Center\; Dot;</span>\underset{\mathrm{<span\; class="notranslate">\; i</span>}<span\; class="notranslate">\; =</span>\mathrm{<span\; class="notranslate">\; 1</span>}}{\overset{{\mathrm{<span\; class="notranslate">\; N</span>}}_{\mathrm{<span\; class="notranslate">\; 1</span>}}}{\mathrm{<span\; class="notranslate">\; \&Sigma;</span>}}}{\mathrm{<span\; class="notranslate">\; Ld</span>}}_{\mathrm{<span\; class="notranslate">\; i</span>}}<span\; class="notranslate">\; +</span>\mathrm{<span\; class="notranslate">\; \&beta;</span>}\underset{\mathrm{<span\; class="notranslate">\; j</span>}<span\; class="notranslate">\; =</span>\mathrm{<span\; class="notranslate">\; 1</span>}}{\overset{{\mathrm{<span\; class="notranslate">\; N</span>}}_{\mathrm{<span\; class="notranslate">\; 2</span>}}}{\mathrm{<span\; class="notranslate">\; \&Sigma;</span>}}}{\mathrm{<span\; class="notranslate">\; Ld</span>}}_{\mathrm{<span\; class="notranslate">\; j</span>}}$

Among them, Ld _i is the downlink time slot load of the first circle of adjacent cells, Ld _j is the downlink time slot load of the second circle of adjacent cells; α is the weighting coefficient of the first circle of adjacent cells to UE downlink time slot interference, β is the weighting coefficient of the interference of adjacent cells in the second circle to UE downlink time slots. N ₁ is the number of adjacent cells in the first circle, and N ₂ is the number of adjacent cells in the first circle.

Preferably, the method for calculating the current downlink time slot load Ld of each neighboring cell of the UE is:

$\mathrm{<span\; class="notranslate">\; Ld</span>}<span\; class="notranslate">\; =</span>\mathrm{<span\; class="notranslate">\; \&gamma;</span>}<span\; class="notranslate">\; \&CenterDot;</span>\underset{\mathrm{<span\; class="notranslate">\; i</span>}<span\; class="notranslate">\; =</span>\mathrm{<span\; class="notranslate">\; 1</span>}}{\overset{{\mathrm{<span\; class="notranslate">\; m</span>}}_{\mathrm{<span\; class="notranslate">\; 1</span>}}}{\mathrm{<span\; class="notranslate">\; \&Sigma;</span>}}}{\mathrm{<span\; class="notranslate">\; Ld</span>}}_{\mathrm{<span\; class="notranslate">\; i</span>}}<span\; class="notranslate">\; +</span>\mathrm{<span\; class="notranslate">\; \&lambda;</span>}\underset{\mathrm{<span\; class="notranslate">\; j</span>}<span\; class="notranslate">\; =</span>\mathrm{<span\; class="notranslate">\; 1</span>}}{\overset{{\mathrm{<span\; class="notranslate">\; m</span>}}_{\mathrm{<span\; class="notranslate">\; 2</span>}}}{\mathrm{<span\; class="notranslate">\; \&Sigma;</span>}}}{\mathrm{<span\; class="notranslate">\; Ld</span>}}_{\mathrm{<span\; class="notranslate">\; j</span>}}$

Among them, M ₁ is the number of adjacent cells with strong signal power to the UE, M ₂ is the number of adjacent cells with relatively weak signal power to the UE, and Ld _i is the number of adjacent cells according to the pilot frequency and angle of arrival AOA The downlink time slot load of the adjacent cell whose signal power to the UE is judged to be strong by measurement, Ld _j is the downlink time slot load of the adjacent cell whose signal power to the UE is relatively weak according to the pilot frequency and AOA measurement, γ and λ are the weighting coefficients of the aforementioned _M1 and _M2 cells respectively.

Preferably, the calculation method of the downlink time slot load Ld _i of the ith cell is:

${\mathrm{<span\; class="notranslate">\; Ld</span>}}_{\mathrm{<span\; class="notranslate">\; i</span>}}<span\; class="notranslate">\; =</span>\frac{{\mathrm{<span\; class="notranslate">\; PTX</span>}}_{\mathrm{<span\; class="notranslate">\; use</span>}}}{{\mathrm{<span\; class="notranslate">\; PTX</span>}}_{\mathrm{<span\; class="notranslate">\; total</span>}}}$

Wherein, PTX _use is the used transmit power of the downlink time slot; PTX _total is the total transmit power allowed to be used in the downlink time slot.

Preferably, the calculation method of the downlink time slot load Ld _i of the ith cell is:

${\mathrm{<span\; class="notranslate">\; Ld</span>}}_{\mathrm{<span\; class="notranslate">\; i</span>}}<span\; class="notranslate">\; =</span>\frac{{\mathrm{<span\; class="notranslate">\; RU</span>}}_{\mathrm{<span\; class="notranslate">\; use</span>}}}{{\mathrm{<span\; class="notranslate">\; RU</span>}}_{\mathrm{<span\; class="notranslate">\; total</span>}}}$

Wherein, RU _use is the number of resource units RU used in the downlink time slot, and RU _total is the total number of RUs in the downlink time slot.

Preferably, the method for calculating the downlink initial transmission power described in step c is:

P _DL-TX = (SIR) _target +L+I

Among them, (SIR) _target is the target signal-to-noise ratio according to the service mapping carried on the channel to meet the service quality QoS requirement; L is the downlink path loss, and I is the downlink time slot interference value.

Preferably, all the operations are performed in the radio network controller RNC. After the RNC calculates the downlink initial transmission power, it further includes: passing the downlink initial transmission power through a radio link channel establishment message, or an RB establishment message, or The physical channel reconfiguration message, or the transport channel reconfiguration message, or the RB reconfiguration message is notified to the base station in the target cell to which the UE is handed over.

The present invention considers the factors of path loss and time slot interference when calculating the downlink initial transmission power, and reasonably calculates the size of the downlink initial transmission power, thereby avoiding the influence caused by too large or too small initial transmission power. In the process of just establishing a physical channel or channel reassignment or handover, even if there is no target downlink time slot interference measurement value reported by the UE, the method of the present invention can be used to calculate the downlink time slot interference, and then the open-loop power control can be used to calculate The downlink initial transmission power ensures the UE's access success rate and service QoS quality requirements, and at the same time avoids causing large interference to other UEs. In this way, the coverage area and capacity of the network can be improved, and the performance of the system can be improved.

Description of drawings

Fig. 1 is a schematic diagram of the relative distance between UE and S ₀ and S _i areas;

Fig. 2 is a schematic flow chart of applying the method of the present invention.

Detailed ways

The present invention will be further described in detail below in conjunction with the accompanying drawings and specific embodiments.

The idea of the present invention is to use the open-loop power control method to calculate the initial downlink transmission power, focusing on the initial channel establishment or handover process and channel reconfiguration process, according to the path loss and surrounding area of the base station signal to the UE location The load of adjacent cells is used to estimate the interference of the target downlink time slot, so as to solve the problem that the UE downlink time slot interference information cannot be obtained in advance.

The formula for calculating the downlink initial transmit power according to the open-loop power control method is as follows:

P _DL-TX = (SIR) _target +L+I (1)

Wherein: (SIR) _target is the target signal-to-noise ratio satisfying the business quality of service (QoS) requirement; L is the downlink path loss, and I is the downlink time slot interference size, that is, the downlink time slot interference value.

Mapping the target SNR according to the bearer service is a well-known technology. The corresponding relationship between the block error rate (BLER) and the signal-to-noise ratio (SIR) under various service configurations is mainly obtained through link simulation and testing, and will not be described in this article.

The calculation method of the downlink path loss L is also a known technology, and the commonly used calculation formula for the size of L is as follows:

L=PTX _PCCPCH -PCCPCH RSCP (2)

Where: PTX _PCCPCH is the reference transmission power of the basic public control channel (PCCPCH), and PCCPCH RSCP is the receiving power of the PCCPCH received by the UE.

I is the interference level of the time slot where the UE is located. When the physical channel is just established or the channel is reconfigured, the UE cannot measure the size of the access time slot and the ISCP of the adjacent cell handover target time slot in advance. Because downlink time slot interference is mainly related to the distance between the UE and the base station (Node B) and the size of the system load, if the distance between the UE and the base station is relatively large, that is, the UE is at the edge of the cell, and the load of the surrounding adjacent cells is relatively large, the UE The interference received by adjacent cells is relatively large; if the distance between the UE and the base station is relatively small, that is, the UE is in the center of the cell, and the load of the surrounding adjacent cells is relatively light, the interference received by the UE will be relatively small. The relationship between downlink time slot interference, path loss and the load of surrounding adjacent cells will be described below.

Usually, the model of the propagation loss is the product of the m-th power of the distance and the normalized value of the lognormal distribution. When the distance between the UE and the base station is r, the propagation loss is proportional to:

L(r, ξ) = r ^m 10 ^ξ/10 (3)

Among them: ξ is the decibel loss caused by shadow, its mean value is 0, and its standard deviation is σ.

Assuming that the cell model is a regular hexagon, let k _u be the average number of UEs in each cell. Since the normalized cell is a regular hexagon, its UE density is:

Referring to Fig. 1, assume that the serving cell where the UE is located is S ₀ , the distance from the UE to the base station NodeB ₀ in the serving cell is r ₀ (x, y), and the distance from the base station NodeB _i of other adjacent cells, such as the S _i cell, to the UE is r _i (x, y), the interference generated by other neighboring cells to the UE is:

$\mathrm{<span\; class="notranslate">\; I</span>}<span\; class="notranslate">\; =</span>\mathrm{<span\; class="notranslate">\; E.</span>}\underset{{\mathrm{<span\; class="notranslate">\; S</span>}}_{\mathrm{<span\; class="notranslate">\; 0</span>}}}{<span\; class="notranslate">\; \&Integral;</span><span\; class="notranslate">\; \&Integral;</span>}<span\; class="notranslate">\; [</span>\frac{{\mathrm{<span\; class="notranslate">\; r</span>}}_{\mathrm{<span\; class="notranslate">\; i</span>}}^{\mathrm{<span\; class="notranslate">\; m</span>}}<span\; class="notranslate">\; (</span>\mathrm{<span\; class="notranslate">\; x</span>}<span\; class="notranslate">\; ,</span>\mathrm{<span\; class="notranslate">\; the\; y</span>}<span\; class="notranslate">\; )</span>{\mathrm{<span\; class="notranslate">\; 10</span>}}^{{\mathrm{<span\; class="notranslate">\; \&xi;</span>}}_{\mathrm{<span\; class="notranslate">\; i</span>}}<span\; class="notranslate">\; /</span>\mathrm{<span\; class="notranslate">\; 10</span>}}}{{\mathrm{<span\; class="notranslate">\; r</span>}}_{\mathrm{<span\; class="notranslate">\; 0</span>}}^{\mathrm{<span\; class="notranslate">\; m</span>}}<span\; class="notranslate">\; (</span>\mathrm{<span\; class="notranslate">\; x</span>}<span\; class="notranslate">\; ,</span>\mathrm{<span\; class="notranslate">\; the\; y</span>}<span\; class="notranslate">\; )</span>{\mathrm{<span\; class="notranslate">\; 10</span>}}^{{\mathrm{<span\; class="notranslate">\; \&xi;</span>}}_{\mathrm{<span\; class="notranslate">\; 0</span>}}<span\; class="notranslate">\; /</span>\mathrm{<span\; class="notranslate">\; 10</span>}}}<span\; class="notranslate">\; ]</span>\mathrm{<span\; class="notranslate">\; \&kappa;dA</span>}<span\; class="notranslate">\; (</span>\mathrm{<span\; class="notranslate">\; x</span>}<span\; class="notranslate">\; ,</span>\mathrm{<span\; class="notranslate">\; the\; y</span>}<span\; class="notranslate">\; )</span><span\; class="notranslate">\; -</span><span\; class="notranslate">\; -</span><span\; class="notranslate">\; -</span><span\; class="notranslate">\; (</span>\mathrm{<span\; class="notranslate">\; 5</span>}<span\; class="notranslate">\; )</span>$

It can be known from formula (5) that the downlink time slot interference is related to the distance from the UE to the base station and the load of adjacent cells. Wherein, κ represents the load of the system, and r ₀ (x, y) and r _i (x, y) represent the position of the UE. Considering the feasibility of engineering implementation, the method of estimating the downlink time slot interference based on the path loss and the load of surrounding cells is adopted. The specific process is as follows:

According to the calculated L, the RNC divides the path loss L between the UE and the base station in a certain order according to the preset downlink path loss threshold {L ₁ , L ₂ ,..., L _n-1 }, such as from near to far, into n types , each category corresponds to a distance S, represented by S1, S2, ..., Sn respectively; n is a positive integer. Of course, it can also be divided in order from far to near. The following is an example in order from near to far.

When L≤L1, S∈S1;

When L1<L≤L2, S∈S2;

...

When L>Ln-1, S∈Sn.

According to the downlink time slot load Ld of the surrounding neighboring cells according to the preset downlink time slot load thresholds {Ld ₁ , Ld ₂ ,...Ld _m-1 }, the RNC puts the downlink time slot load Ld in a certain order, such as from light to Heavy, divided into m categories, each category corresponds to a downlink time slot load level D, respectively denoted by D1, D2, ..., Dm, m is a positive integer. Of course, it can also be divided in order from heavy to light. The following is an example in order from light to heavy.

When Ld≤Ld1, Ld∈D1;

When Ld1<Ld≤Ld2, Ld∈D2;

...

When Ld>Ldm-1, Ld∈Dm.

A total of m×n combinations are obtained, and each combination S _i D _j corresponds to a reference value of interference I of a downlink time slot.

In the TD-SCDMA system, the downlink time slot load Ld can be calculated according to the transmit power of the downlink time slot or the ratio of the allocated channel number of the downlink time slot to the total number of downlink time slot channels.

The downlink timeslot interference is affected by the loads of all surrounding adjacent cells, and the downlink timeslot load of each adjacent cell has different influences on the downlink timeslot interference of the UE.

Assuming that the UE's downlink time slot interference is mainly affected by the surrounding N cells, the method of evaluating the load of the surrounding adjacent cells is as follows:

$\mathrm{<span\; class="notranslate">\; Ld</span>}<span\; class="notranslate">\; =</span>\underset{\mathrm{<span\; class="notranslate">\; i</span>}<span\; class="notranslate">\; =</span>\mathrm{<span\; class="notranslate">\; 1</span>}}{\overset{\mathrm{<span\; class="notranslate">\; N</span>}}{\mathrm{<span\; class="notranslate">\; \&Sigma;</span>}}}{\mathrm{<span\; class="notranslate">\; \&alpha;</span>}}_{\mathrm{<span\; class="notranslate">\; i</span>}}<span\; class="notranslate">\; \&CenterDot;</span>{\mathrm{<span\; class="notranslate">\; Ld</span>}}_{\mathrm{<span\; class="notranslate">\; i</span>}}<span\; class="notranslate">\; -</span><span\; class="notranslate">\; -</span><span\; class="notranslate">\; -</span><span\; class="notranslate">\; (</span>\mathrm{<span\; class="notranslate">\; 6</span>}<span\; class="notranslate">\; )</span>$

Among them: Ld _i is the downlink time slot of the i-th cell, α _i is the weighting coefficient of the downlink time slot load of the cell on the downlink time slot interference of the UE, and α _i represents the degree of influence of the cell on the UE interference.

Since the downlink beamforming technology is adopted in the TD-SCDMA system, the RNC can obtain the angle of arrival (AOA) information of the UE, and the RNC can judge the relative position relationship between a certain adjacent cell and the UE according to the AOA information of the UE. Therefore, the size of α _i in the formula (6) is related to two factors, one is the distance between the UE and the base station of a certain neighboring cell, and the other is the relative position relationship between the UE and the base station of a certain neighboring cell.

If it is assumed that the adjacent two circles of cells play a leading role in the downlink time slot interference of the UE. And it is assumed that there are N ₁ adjacent cells in the first circle, and it is assumed that the load of the adjacent cells in the first circle has the same impact on the UE's downlink time slot interference; there are N ₂ adjacent cells in the second circle, and it is assumed that the second The impact of the load of adjacent cells in the circle on the UE's downlink time slot interference is also the same, so the method for evaluating the load of the surrounding adjacent cells is as follows:

$\mathrm{<span\; class="notranslate">\; Ld</span>}<span\; class="notranslate">\; =</span>\mathrm{<span\; class="notranslate">\; \&alpha;</span>}<span\; class="notranslate">\; \&CenterDot;</span>\underset{\mathrm{<span\; class="notranslate">\; i</span>}<span\; class="notranslate">\; =</span>\mathrm{<span\; class="notranslate">\; 1</span>}}{\overset{{\mathrm{<span\; class="notranslate">\; N</span>}}_{\mathrm{<span\; class="notranslate">\; 1</span>}}}{\mathrm{<span\; class="notranslate">\; \&Sigma;</span>}}}{\mathrm{<span\; class="notranslate">\; Ld</span>}}_{\mathrm{<span\; class="notranslate">\; i</span>}}<span\; class="notranslate">\; +</span>\mathrm{<span\; class="notranslate">\; \&beta;</span>}\underset{\mathrm{<span\; class="notranslate">\; j</span>}<span\; class="notranslate">\; =</span>\mathrm{<span\; class="notranslate">\; 1</span>}}{\overset{{\mathrm{<span\; class="notranslate">\; N</span>}}_{\mathrm{<span\; class="notranslate">\; 2</span>}}}{\mathrm{<span\; class="notranslate">\; \&Sigma;</span>}}}{\mathrm{<span\; class="notranslate">\; Ld</span>}}_{\mathrm{<span\; class="notranslate">\; j</span>}}<span\; class="notranslate">\; -</span><span\; class="notranslate">\; -</span><span\; class="notranslate">\; -</span><span\; class="notranslate">\; (</span>\mathrm{<span\; class="notranslate">\; 7</span>}<span\; class="notranslate">\; )</span>$

Among them: Ld _i is the downlink time slot load of the first circle of adjacent cells, Ld _j is the downlink time slot load of the second circle of adjacent cells; α is the weighting coefficient of the first circle of adjacent cells to UE downlink time slot interference, β is the weighting coefficient of the interference of adjacent cells in the second circle to UE downlink time slots, usually α is greater than or equal to β, that is, α≥β.

If during the UE handover process, the RNC judges that the signal power from the M ₁ cells to the UE is very strong through the pilot measurement and AOA information, that is, the generated downlink time slot interference is also strong _; If the signal power to the UE is relatively weak, the method of evaluating the load of surrounding adjacent cells is as follows:

$\mathrm{<span\; class="notranslate">\; Ld</span>}<span\; class="notranslate">\; =</span>\mathrm{<span\; class="notranslate">\; \&gamma;</span>}<span\; class="notranslate">\; \&Center\; Dot;</span>\underset{\mathrm{<span\; class="notranslate">\; i</span>}<span\; class="notranslate">\; =</span>\mathrm{<span\; class="notranslate">\; 1</span>}}{\overset{{\mathrm{<span\; class="notranslate">\; m</span>}}_{\mathrm{<span\; class="notranslate">\; 1</span>}}}{\mathrm{<span\; class="notranslate">\; \&Sigma;</span>}}}{\mathrm{<span\; class="notranslate">\; Ld</span>}}_{\mathrm{<span\; class="notranslate">\; j</span>}}<span\; class="notranslate">\; +</span>\mathrm{<span\; class="notranslate">\; \&lambda;</span>}\underset{\mathrm{<span\; class="notranslate">\; j</span>}<span\; class="notranslate">\; =</span>\mathrm{<span\; class="notranslate">\; 1</span>}}{\overset{{\mathrm{<span\; class="notranslate">\; m</span>}}_{\mathrm{<span\; class="notranslate">\; 2</span>}}}{\mathrm{<span\; class="notranslate">\; \&Sigma;</span>}}}{\mathrm{<span\; class="notranslate">\; Ld</span>}}_{\mathrm{<span\; class="notranslate">\; j</span>}}<span\; class="notranslate">\; -</span><span\; class="notranslate">\; -</span><span\; class="notranslate">\; -</span><span\; class="notranslate">\; (</span>\mathrm{<span\; class="notranslate">\; 8</span>}<span\; class="notranslate">\; )</span>$

Among them: Ld _i is the downlink time slot load of the adjacent cell whose signal power to the UE is judged to be strong according to the pilot frequency and AOA measurement, and Ld _j is the relatively weak signal power to the UE judged according to the pilot frequency and AOA measurement γ and λ are the weighting coefficients of the aforementioned M ₁ and M ₂ cells respectively, usually γ is greater than or equal to λ, that is, γ≥λ.

Since the meanings represented by Ld _j and Ld _i are the same, only Ld _i is used as an example for illustration below.

There are two ways to calculate the downlink time slot load Ld _i of each cell, one is based on the transmit power of the downlink time slot, and the other is based on the ratio of the number of allocated channels in the downlink time slot to the total number of channels in the downlink time slot. Therefore, the calculation method of Ld _i in the formulas (6), (7), and (8) is as follows:

method one: ${\mathrm{Ld}}_i=\frac{{\mathrm{PTX}}_{\mathrm{use}}}{{\mathrm{PTX}}_{\mathrm{total}}}---\left(9\right)$

Where: PTX _use is the used transmit power of the downlink time slot; PTX _total is the total transmit power allowed to be used in the time slot.

Method Two: ${\mathrm{Ld}}_i=\frac{{\mathrm{RU}}_{\mathrm{use}}}{{\mathrm{RU}}_{\mathrm{total}}}---\left(10\right)$

Where: RU _use is the number of resource units (RU) used in the downlink time slot, and RU _total is the total number of RUs in the downlink time slot.

That is to say, an M×N downlink slot interference matrix list (ISCP) _M×N is preset in the RNC, which includes the distance S between the UE and the base station and the downlink slot load level D of the surrounding adjacent cells. The corresponding relationship between the item and the interference value I of the downlink time slot.

When the UE initiates an initial call or switches the UE to a new cell, the current distance S between the UE and the base station is obtained according to the downlink path loss, and the downlink time slot of the UE's current neighboring cell is estimated according to the downlink time slot load Ld of the neighboring cell Load level D: Obtain the downlink time slot interference of the UE by querying the corresponding relationship of the downlink time slot interference matrix list. For example, by looking up the row S _i and column D _j in the matrix list, find the corresponding interference value I in the distance array table, and then put I into the formula (1), the initial transmission of the downlink can be obtained power.

The downlink time slot load Ld of the adjacent cell is calculated by formula (6) or formula (7) or formula (8).

The present invention is described again below in conjunction with embodiment.

Assuming that a voice UE needs to be handed over, calculate its downlink initial transmit power in the target time slot of the handover target cell, see Figure 2, the specific process is as follows:

Step 201 , according to the service carried on the channel, map to satisfy the target signal-to-noise ratio (SIR) _target of the service QoS. Calculate the downlink path loss for the base station signal to reach the location of the UE terminal UE, the specific calculation method is as formula (2), and will not be repeated here.

The above two-step calculations are not in strict order.

Step 202: Determine the UE's downlink time slot interference value according to the downlink path loss and loads of surrounding cells. Specifically in this example:

A 3×3 downlink slot interference matrix list is preset, which includes the correspondence between the distance S between the UE and the base station, the downlink slot load level D of the surrounding adjacent cells, and the downlink slot interference; that is, the downlink The path loss threshold {L ₁ , L ₂ }, the downlink path loss threshold is divided into three categories according to a certain order, such as near, middle and far, and each category corresponds to a distance S, such as represented by S1, S2, and S3 respectively, And each category corresponds to a downlink path loss threshold interval; set the downlink time slot load threshold {Ld ₁ , Ld ₂ }, and divide the downlink time slot load threshold into three categories according to a certain order, such as from light to heavy, Each category corresponds to a downlink time slot load level D, as represented by D1, D2, and D3 respectively, and each category corresponds to a downlink path loss threshold interval. Right now

When _L≤L1 , S∈S1;

When L ₁ <L≤L ₂ , S∈S2;

When L>L ₂ , S∈S3;

When Ld≤Ld ₁ , Ld∈D1;

When Ld ₁ <Ld≤Ld ₂ , Ld∈D2;

When Ld>Ld ₂ , Ld∈D3;

And S1, S2, S3 and D1, D2, D3 are respectively combined, and there are 9 kinds of combination results, and each combination S _i D _j corresponds to a downlink time slot interference value I reference value.

Calculate the current downlink path loss value L of the UE, determine the threshold interval where the current downlink path loss value L of the UE is located according to the downlink path loss threshold, and then obtain the distance S between the UE and the base station according to the threshold interval.

Calculate the current downlink timeslot load Ld of the UE, determine the threshold interval where the current downlink timeslot load Ld of the UE is located according to the downlink timeslot load threshold, and then obtain the downlink timeslot load level D according to the threshold interval. Wherein, the current downlink time slot load Ld of the UE can be calculated by formula (6), (7) or (8).

According to the obtained distance S and downlink time slot load level D, query the downlink time slot interference matrix list to obtain the downlink time slot interference value I.

Step 203: Calculate the downlink initial transmit power by using the open-loop power control method, ie formula (1), according to the target SNR, downlink path loss and UE's downlink timeslot interference value.

All operations of calculating the downlink initial transmission power are performed in the RNC. After the RNC calculates the downlink initial transmission power, the downlink initial transmission power is passed through a radio link channel establishment message, or an RB establishment message, or a physical channel reconfiguration message , or transmit the channel reconfiguration message, or notify the RB reconfiguration message to the base station in the target cell to which the UE is handed over.

The present invention considers the factors of path loss and time slot interference when calculating the downlink initial transmission power, and can calculate the size of the downlink initial transmission power more accurately and reasonably, thereby avoiding the influence caused by too large or too small initial transmission power. In the process of just establishing a physical channel or channel reassignment or handover, even if there is no target time slot interference measurement value reported by the UE, the method of the present invention can be used to estimate the downlink time slot interference, thereby assisting open-loop power control and ensuring The UE's access success rate and service QoS quality requirements can be avoided while causing large interference to other UEs. In this way, the coverage area and capacity of the network can be improved, and the performance of the system can be improved.

The above descriptions are only preferred embodiments of the present invention, and are not intended to limit the protection scope of the present invention. Any modification, equivalent replacement, improvement, etc. made within the spirit and principles of the present invention are included in the protection scope of the present invention.

Claims (12)

1. A method for determining downlink initial transmission power is characterized by comprising the following steps:

a. calculating the downlink path loss of a base station signal reaching the position of the user terminal UE;

b. determining a downlink time slot interference value of the UE according to the downlink path loss and the load of surrounding cells;

c. and calculating the downlink initial transmitting power according to the downlink time slot interference value.

2. The method of claim 1, wherein the method for calculating the downlink path loss in step a is as follows:

reference transmit power PTX using a primary common control channel PCCPCH_PCCPCHThe received power PCCPCH RSCP of the PCCPCH received by the UE is subtracted, and the difference is the downlink path loss.

3. The method of claim 1, wherein the step b of determining the downlink timeslot interference comprises:

presetting a downlink time slot interference matrix list, wherein the list comprises the corresponding relation between the distance S between the UE and the base station and the downlink time slot load grade D of the surrounding adjacent cells and the downlink time slot interference;

estimating the current distance S between the UE and the base station according to the downlink path loss, and estimating the downlink time slot load grade D of the current adjacent cell of the UE according to the downlink time slot load Ld of the adjacent cell; and acquiring the downlink time slot interference of the UE by inquiring the corresponding relation of the downlink time slot interference matrix list.

4. The method of claim 3, wherein the estimating the distance S between the UE and the base station according to the downlink path loss comprises:

presetting a downlink path loss threshold { L) comprising one or more downlink path loss values₁，L₂，…，L_n-1}; dividing the downlink path loss threshold values into at least one class according to a certain sequence, wherein each class corresponds to a distance S and corresponds to a downlink path loss threshold value interval;

and calculating the current downlink path loss value L of the UE, determining a threshold interval where the current downlink path loss value L of the UE is located according to the downlink path loss threshold, and obtaining the distance S between the UE and the base station according to the threshold interval.

5. The method according to claim 3, wherein the estimating the downlink timeslot load level D of the current neighboring cell of the UE according to the downlink timeslot load Ld of the neighboring cell comprises:

presetting a downlink time slot load threshold { Ld) containing one or more downlink time slot load values₁，Ld₂，…Ld_m-1}; dividing the downlink time slot load threshold into at least one class according to a certain sequence, wherein each class corresponds to a downlink time slot load grade D and a downlink path loss threshold interval;

and calculating the current downlink time slot load Ld of the LE, determining a threshold interval where the current downlink time slot load Ld of the UE is located according to the downlink time slot load threshold, and obtaining the current downlink time slot load grade D according to the threshold interval.

6. The method according to claim 5, wherein the method for calculating the current downlink timeslot load Ld of the UE is:

<math> <mrow> <mi>Ld</mi> <mo>=</mo> <munderover> <mi>&Sigma;</mi> <mrow> <mi>i</mi> <mo>=</mo> <mn>1</mn> </mrow> <mi>N</mi> </munderover> <msub> <mi>&alpha;</mi> <mi>i</mi> </msub> <mo>&CenterDot;</mo> <msub> <mi>Ld</mi> <mi>i</mi> </msub> </mrow> </math>

wherein, Ld_iIs the downlink time slot load, α, of the ith neighbor cell_iThe weight coefficient of the interference of the downlink time slot load of the adjacent cell to the downlink time slot of the UE; and N is the number of adjacent cells.

7. The method according to claim 5, wherein the method for calculating the current downlink timeslot load Ld of the UE is:

<math> <mrow> <mi>Ld</mi> <mo>=</mo> <mi>&alpha;</mi> <mo>&CenterDot;</mo> <munderover> <mi>&Sigma;</mi> <mrow> <mi>i</mi> <mo>=</mo> <mn>1</mn> </mrow> <msub> <mi>N</mi> <mn>1</mn> </msub> </munderover> <msub> <mi>Ld</mi> <mi>i</mi> </msub> <mo>+</mo> <mi>&beta;</mi> <munderover> <mi>&Sigma;</mi> <mrow> <mi>j</mi> <mo>=</mo> <mn>1</mn> </mrow> <msub> <mi>N</mi> <mn>2</mn> </msub> </munderover> <msub> <mi>Ld</mi> <mi>j</mi> </msub> </mrow> </math>

wherein, Ld_iIs the downlink time slot load, Ld, of the first circle of adjacent cells_jIs the downlink timeslot load of the second circle of adjacent cells; alpha is the weighting coefficient of the first circle of adjacent cells to the downlink time slot interference of the UE, beta is the weighting coefficient of the second circle of adjacent cells to the downlink time slot interference of the UE, N₁Is the number of first turn neighbor cells, N₂Is the number of adjacent cells of the first ring.

8. The method according to claim 5, wherein the method for calculating the downlink timeslot load Ld of each current neighboring cell of the UE comprises:

<math> <mrow> <mi>Ld</mi> <mo>=</mo> <mi>&gamma;</mi> <mo>&CenterDot;</mo> <munderover> <mi>&Sigma;</mi> <mrow> <mi>i</mi> <mo>=</mo> <mn>1</mn> </mrow> <msub> <mi>M</mi> <mn>1</mn> </msub> </munderover> <msub> <mi>Ld</mi> <mi>i</mi> </msub> <mo>+</mo> <mi>&lambda;</mi> <munderover> <mi>&Sigma;</mi> <mrow> <mi>j</mi> <mo>=</mo> <mn>1</mn> </mrow> <msub> <mi>M</mi> <mn>2</mn> </msub> </munderover> <msub> <mi>Ld</mi> <mi>j</mi> </msub> </mrow> </math>

wherein M is₁For the number of neighboring cells with strong signal power to the UE, M₂Number of neighboring cells, Ld, with relatively weak signal power to the UE_iIs the downlink time slot load, Ld, of the adjacent cell with strong signal power to the UE, which is judged according to the measurement of the pilot frequency and the arrival angle AOA_jJudging the downlink time slot load of the adjacent cell with relatively weak signal power to the UE according to the pilot frequency and AOA measurement, wherein gamma and lambda are respectively M₁And M₂Weighting coefficients of the cells.

9. The method according to claim 6, 7 or 8, characterized in that the downlink timeslot load Ld of the ith cell_iThe calculation method comprises the following steps:

${\mathrm{Ld}}_i=\frac{{\mathrm{PTX}}_{\mathrm{use}}}{{\mathrm{PTX}}_{\mathrm{total}}}$

wherein, PTX_useIs the used transmit power of the downlink timeslot; PTX_totalIs the total transmit power allowed to be used by the downlink time slot.

10. The method according to claim 6, 7 or 8, characterized in that the downlink timeslot load Ld of the ith cell_iThe calculation method comprises the following steps:

${\mathrm{Ld}}_i=\frac{{\mathrm{RU}}_{\mathrm{use}}}{{\mathrm{RU}}_{\mathrm{total}}}$

wherein, RU_useIs the number of resource units RU used in the downlink time slot_totalIs the total number of RUs in the downlink timeslot.

11. The method of claim 1, wherein the method for calculating the downlink initial transmit power in step c comprises:

P_DL-TX＝(SIR)_target+L+I

wherein, (SIR)_targetA target signal-to-noise ratio mapped according to a service carried on a channel to meet a service quality of service (QoS) requirement; l is the downlink path loss, and I is the downlink time slot interference value.

12. The method of claim 1, wherein all the operations are performed in a radio network controller RNC, and after the RNC calculates the downlink initial transmission power, the method further comprises: and informing the downlink initial transmitting power to a base station in a target cell switched by the UE through a wireless link channel establishment message, or an RB establishment message, or a physical channel reconfiguration message, or a transmission channel reconfiguration message, or an RB reconfiguration message.

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